There is still considerable uncertainty about the accurate classification of human hematopoietic tumors, as well as considerable variability in prognosis and in response to treatment, not only among different hematopoietic tumors, but also within any one diagnostic category. More precise diagnosis and definition of the relationships between these tumors is therefore important, not only in terms of reaching a clearer understanding of their cellular origins, but also in predicting prognosis, evaluating current treatment regimens, and developing more effective methods of therapy. The first objective of this program project is to conduct a comprehensive clinical-investigative study of all varieties of hematopoietic tumors, with emphasis on correlating the results of newer immunological, biochemical, cytogenetic, ultrastructural, kinetic and various functional tests which have potential clinical relevance with classical hematological and pathological diagnostic criteria, and with clinical data on staging response to treatment and survival. The eventual goal is to develop a more accurate and meaningful classification and more rational and effective treatment programs based on this classification. The second purpose is to coordinate all basic research efforts within the Center which are aimed at reaching a better understanding or improving the treatment of hematopoietic tumors, regardless of whether this research has any immediate clinical relevance.